I feel like an idiot but I still have to share

Well I have spent 6-7 weeks trying to figure out why my bike was running extremely lean. It turns out that I installed the needle valve upside down in the FCR carb :D

This part is number 11 in the following link:

Originally I had a fuel contamination problem which clogged up my pilot and main jets. This happened twice. After the second time I decided to pull the carb and the fuel tank and clean them thoroughly. Much to my surprise when I put everything back together, the bike ran slightly leaner than before I pulled it apart.

I don't even want to reflect on all the things I checked and tested to find my suspected air leak/fuel restriction :D

After exhausting my efforts on the carb I started looking at valve clearance. I did find that my new titanium valves were all on the tight side of the tolerance or out of tolerance on the tight side. I have never had to make an adjustment on my '99 or '00 so if you have an '01 you might want to check.

Anyway, just thought I'd share my experience with all of you. Hopefully I can spare someone else a lot of frustration. Now I can get back to testing BK's accelerator pump mod. :) I just installed it when I started having the contamination problem.

See Ya,



Pretty fly for a fat guy!

[This message has been edited by Thumper448 (edited 06-23-2001).]

I just looked up that link you added and it brought back a post from a few weeks ago. Someone posted a problem concerning his carb that he had just disassembled to clean and when he reassembled it, the engine ran terribly. As it happened, I had just did maintenance on my carb and noticed how this particular part could be accidently resinstalled upside as you described. So, don't feel bad...it's easy to do.

Let me see if I can guess how it happened. You disassembled the carb to the point that you yanked the throttle valve assembly from the carb throat....and then the needle valve fell out onto the floor or workbench? Probably startled you...didn't expect it.....as did me. Now, you have this plate to put back in and it looks rather plain, plus it will fit two ways....correctly and upside down. The reason I know this is that I when I had my carb apart for cleaning, the plate fell out on my workbench and I checked it over thoroughly before reassembling. Luckily, I knew that the cutaway went at the bottom, but for curiosity, I tested to see if it could be assembled upside down...and it could. When I saw a fellow 426 owner describe his problem, it occured to me that he possibly could have made this error. He did.

The FCR carb is not a carb to be taken lightly.

I did the same thing (accidently) through efforts trying to get my bike to stop running so rich. I thought I stumbled onto something magical!!!!!

All my bike would do was pop and snap when I revved it (on the stand) though, so I knew something was not right. At least I got rid of that nasty black spark plug though.....

good luck.


I did the same thing and it made me NUTS!

Took the carb apart because I wanted to see where the needle clip was and put it back together without changing anything.

Could barely get it started and it would pop and backfire all the time. Cleaned the carb and it got a little better (dont know why though) and went to the track the next day thinking it was fixed.

Was still lean as could be at idle and fine everywhere else so I rode anyway, at the end of the day, a buddy of mine wanted to see where the pilot and slow jets were on the carb and since he had his manual handy I flipped to the carb explosion and showed him. It took me about .5 seconds to see the plate was installed upside down when I looked at the diagram. Flipped it back over and ta-da!

I felt like an idiot too but intuitively it really seemed like that was the way it should go back in. Also since I dropped the plate when I took the slide out, I never had a chance to see it during dis-assembly.

Oh well, it happens!

Dave S

A lot of people have reported over the past couple years of having this part of their carb slide break. Maybe it is because they ran it too long up-side-down?


'92 GSXR 7/11 (But I never ride it so you should buy it...)

'99 YZ400F 'cause thumpers rule and two strokes drool!

'02 Honda CR450F - Coming in October!!!

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now